1. Unit 4: Momentum & Impulse I can calculate momentum using p=mv I can calculate impulse using I = Ft

2. Momentum  Momentum = Mass in motion  Any object that is moving has momentum

3. Demo Which is harder to stop? vs Which is harder to stop? fast slow

4. What is the equation for momentum?  Momentum depends on the mass of the object and the velocity at which its traveling  Momentum is DIRECTLY proportional to mass and velocity. (if mass, momentum, if velocity, momentum ) Momentum = mass x velocity p = m x v

5. What are the units for momentum? p = m x v Momentum = mass x velocity kg∙m/s = kg x m/s

6. What are the units for momentum?  Units = kg∙m/s MeasurementUnit DistanceMeters (m) TimeSeconds (s) Velocitym/s Accelerationm/s 2 ForceNewton (N) (kg∙m/s 2 ) Momentumkg∙m/s

7. Think, Pair, Share OR WHICH HAS MORE MOMENTUM?

8. What if I tell you….  Mass of the bullet = 0.045 kg  Velocity of bullet = 3000 m/s  Mass of elephant= 1250 kg  Velocity of elephant= 0.108 m/s

9. And the winner is…. p = mv  p bullet = (.045 kg)(3000m/s) = 135 kg∙m/s  p elephant = (1250 kg)(.108 m/s) = 135 kg∙m/s EQUAL!!

10. Work it Out Determine the momentum of …  60-kg halfback moving at 9 m/s  1000-kg car moving at 20 m/s.  40-kg freshman moving at 2 m/s. A bicycle has a momentum of 24 kgm/s. What momentum would the bicycle have if it had …  twice the mass and was moving at the same speed?  the same mass and was moving with twice the speed?  one-half the mass and was moving with twice the speed?  three times the mass and was moving with one-half the speed?  three times the mass and was moving with twice the speed?

11. What is impulse?  Impulse is the change in an object’s momentum I = F ∙ t = m ∙ ∆v impulse momentum *when mass stays the same

12. What are the units for impulse?  Units = N∙s or kg∙m/s MeasurementUnit DistanceMeters (m) TimeSeconds (s) Velocitym/s Accelerationm/s 2 ForceNewton (N) (kg∙m/s 2 ) Momentumkg∙m/s ImpulseN∙s or kg∙m/s

13. Examples

14. Quick Checks  How do you stop an object with momentum?  Is it harder to stop an object with more mass or less mass?  Compare the forces I would need to exert to stop a bowling ball and a tennis ball traveling at the same speed.  What happens when an unbalanced force acts on an object?  What is acceleration?

15. Quick Checks  When an object’s velocity changes, so does its…  What is the name for a change in momentum?  What is the equation we use to represent impulse?  Give me 2 examples of impulses.

16. Practice  During batting practice, a 0.30-kg baseball is hit with a bat that exerts a force of 350 N on the ball. The ball left the bat at 80 m/s. If the incoming pitch was traveling at 60 m/s, how long did the ball stay in contact with the bat?  Solve and Explain how the problem above is an example of impulse.

17. Homework  Book p. 138 #2-9, 24-28, 32, 45